Solution 7

SFKX = Four-digit number = S x 1000 + F x 100 + K x 10 + X x 1

( S x 1000 + F x 100 + K x 10 + X ) - ( S + F + K + X ) x 100 = 7236

From here , we can confirm K an X to be 3 and 6 respectively .This is because of the x 100 .( S + F + K + X ) x 100 will always end with 2 zeroes behind .Therefore K and X minus 0 each , is still K and X which is 3 and 6 respectively .

Now we know SFKX = SF36 .Since F doesn't affect the result of 7236, we exclude F from the calculation .It can be any whole number from 0 to 9 .To be simple , we use F = 0 in this case .Focusing on S , we substitute F = 0 , K = 3 and X = 6 to form this statement .